Electric furnace



Feb. 25, 1930. A. STANSFIELD ELECTRIC FURNACE Filed March 22, 1929 3 Sheets-Sheet 1 INVENTOR- 19L FRED STflNSF/ELII Feb. 25, 1930. A. STANSFIELD ELECTRIC FURNACE Filed March 22, 1929 3 Sheets-Sheet 2 llllllL INVENTUR 14L FRED ST/INSFIELD.

HTTORNEX .l atented Feb; 25,

FURNACE A lication filed. March 2% 1&29.

This invention relates to improvements in the process of electric smelting of iron ores and of the apparatus which is required for that purpose.

T he objects of the invention are to provide -a method and means for the reduction and electric smelting of iron ores, which will overcome many of the difiiculties and disadvantages of present methods, which will utilize more completely and more economically the heat and gases given off from the electric furnace in preparing the charge for final conversion in such furnace, which will permit the treatment of finely divided ores, concentrates and iron sands without the necessity of briquetting, and also the use of fuel in powdered form in the mixture to be treated, which reduces the requirement of mechanical power to a minimum, and WhlClilS carried out in an apparatus of simple and durable construction, operated With the minimum of attention.

Further objects will be set forth hereinafter.

The invention consists briefly in preheating and effecting the partial reduction of the charge by means of the gases given o l in the electric furnace as the charge descends over a series of inclined surfaces in thin layers over which the gases flow in counter current whereby it is thoroughly pepared for the final operation in the electric furnace.

Reference Will'be made to the accompanying drawings in which Figure l is a vertical cross section.

Figure 2 is a vertical cross section. in three parts, A on the line 22, in Figure on the line W 2, iuFigure l, G on line 2"-2., in Figure 1.

Figure 3 shows a type of stack with gravity teed.

Figure 4 shows a novel form of furnace teed,

Figures fraud 6 show of employed,

he :ralres Serial No. 349,107.

Hitherto the treatment of ore, in preparation for electric smelting, by the gases and heat they carry from the electric furnace, has usually followed one of two methods.

First wmf/20(Z.-The ore mixture has been fed to the furnace down through a vertical or substantially vertical shaft, through which the gases ascend. This necessitates a mixture of a coarse character, in order to permit the gases to make their way up through it, and prevents the treatment of fines, concentrates or powdered material unless it is first briquettcd. In this process it is impossible for chemical reasons, to utilize the gases at all completely, and the escaping partly used 69 gases represent a serious loss.

Second meth0cZ.-ln this, the ore mixture is passed through rotating drums in comparatively thin layers, and is heated by the gases either directly or indirectly, using the counter current system. By this process the gases can he used more completely, but the apparatus occupies a large space leading to needless loss of heat, requires a considerable amount of mechanical power and is costly in its inre stallment and upkeep. Attempts have been made to combine these methods but Without success in overcoming their disadvantages to any extentv By means of this invention, while securing the advantages of both the above mentioned methods, their disadvantages are to a great extent avoided.

Tit is specially designed totreat powdered m material to provide a free flow the gases, my to reduce the use of mechanical power to a minimum, and to result in a uniform product Well prepared for the final treatment in the electric furnace.

The particular details of construction the terms of apparatus described herein 7 shown in the drawings, are not in any way to be considered as limiting the scope of invention, but merely as illustrations of prac tical means by which the invention can be carried out.

In Figure 1 the electric furnace 1 is shown between two vertical stacks 22 of similar design. The electrodes 10 are supported in water cooled stuffing boxes 11 set in the arched roof 12. The usualtapping holes 13 are provided to enable the molten metal and the slag to be drawn off.

The stacks 22 have inner and outer walls 20, end walls 21, and a series of partition walls 22 which divides the stack into vertical chambers. Supported on ledges or brackets 23 on the sides of the partition walls 22, are a series of inclined floors 24 which extend from the side walls 20 downwards but not as far as the wall opposite, the gap between their lower ends 240 and the side wall 20 providing openings through which the material being treated, falls to the top of the floor below. The partition walls 22 have a series of openings 220, 221', 222, 223 and 224 which provide continuous flues between the end walls 21 over each floor 24. By-pass flues 210 connect the adjacent levels alternately to supply an unobstructed channel for the gases to c1rculate upwards through the stack 2. Openings 211 are provided to the upper ends of the tines 210, in order to permit air and fuel to be admitted to assist in the treatment as required. The inclined bottom floor 241 extends to the edge of the side wall 15 of the furnace 1. The top floor 242 forms the hopper wall and is mounted at a steeper angle than the floors 24. The side walls 20 have slots through which suitable sliding gates 25 can be inserted, whereby the flow of the ore mixture can be held back on any floor, when required. A series of rakes 26 operated through the side walls 20, and having bevelled cross bars 260, supported on the floors 24 are provided with means to recipro cate them at a controlled speed. This means may take the form of oscillating shafts 261 outside the walls 20, linked to therakes 26. The rakes 26 may be water cooled if neces sary. The lower floor 241 has a battle late 243 which extends from the bottom 0 the inner wall 20 parallel t the lower floor 241 towards the outerwall 2 but only far enough to provide an entrance to the chamber below the first inclined floor 24.

In Figure 3 a. form of construction is shown of a stack adapted for the descent ofthe ore mixture over the floors by gravity alone In this design, the floors 24 are inclined at a greater angle and are mounted in oppositely inclined pairs. The hopper has a central outlet, between the edges of the floors 242 242. The pair of floors below are inclined outwardly towards the side walls 20, with outlets at their lower edges. The next pair of floors incline inwardly to a central out let, and the alternation continues to the bottom floor.

The bottom floor has a central outlet, and the outer incline 227 may be built in as part of the stack wall, the outlet feeds to an inclined passageway leading to the ed e of the furnace wall 15. A similar series of vertical partition walls 22 with openings 220, 221, 222, 223 and 224 provide continuous flues between the end walls with by-pass passages connecting adjacent levels alternatel to furnish an obstructed channel from the furnace 1 to the outlet flue 213. Sliding gates 25 and poking holes 28 are provided in the side walls 20 to regulate and control the downward flow of the ore mixture on the floors 24.

In Figure 4, a modification of the feed passage to the furnace is shown. In this construction the feed floor 241 is inclined to enter the side of the furnace chamber and to direct the feed to the zone of greatest heating elliciency. This floor 241 is provided with pok ing holes 28, in the wall of the stack.

In Figures 1, 2 and 4, the furnace is shown with a bed of lump carbon on which the ore mixture is fed, but this feature is not to be included in the present specification as it is the subject matter of a separate specification.

Employing apparatus constructed on lines such as are above described and shown in the drawings,- the operation of the invention is as follows:

As the mixture of ore, fuel and flux gradually descends the stack it is dried and heated, reaching finally a temperature of about 800 to 1000 (I, the fuel is carbonized, giving off any volatile ingredients, the limestone is partly calcined and the ore itself is chemically reduced by reaction with the gases and the carbon of the fuel so that the iron oxide has all been reduced to the state of ferrous oxide and this in large measure has been reduced to metallic iron.

In the electric furnace the remainder of the ferrous oxide is reduced by means of carbon as shown by the equation;

FeO+0=Fe+CO (1) Silicon is also formed by the reduction of a part of the silica in the ore as shown by the equation;

SiO +2C=Si+2CO (2) and sulphur is removed from the iron by the action of carbon and lime as shown by the equation FeS+CaO+C=Fe+CaS+CO 3 upwards overand across the ore mixture on weapon pulverized coal may be introduced for the purpose of increasing the temperature ofthe ore charge in the stack, but care must be taken not to heat the charge to a temperature at which it becomes sticky before it enters the furnace. I

The gaseous products of combustion pass the floors in the stack and finally, after heating the fioor of the hopper they pass ofi through the outlet flue.

The ore mixture which receives a preliminary heating in thehopper descends over the inclined floors in thin layers which are subjected to'the heat at increasing temperatures of the upward current of gases until it reaches the electric furnace.

The'layers of ore mixture on the inclined floors are kept in motion by the rakes which reciprocate and which are protected from the heated gases by the covering of ore mixture, but which may be provided with suitable cooling means if necessary. A particular feature of the descent of the ore mixture from one floor to the one below, is that the layers are reversed and thetop of the layer on one floor becomes the bottom of the layer 011 the next floor below. This frequent reversal results in a thorough and even heating of theore mixture and in particular it obviates any tendency of the charge to become unmixed through the lighter ingredients (coal etc.) coming to the surface.

The. effect of this treatment of the 'ore mixture is such that by the time it has reached the lower floor, it has been to a large extent reduced and it enters the furnace in the form of iron and flux ready to be rapidlymelted and converted into molten iron and slag.

By means of the two stacks and their efficient operation in preparing for the final treatment in the furnace, the capacity is greatly increased and the output is at a high rate. t

The losses from unburnt gases and from wasted heat are reduced to a minimum and the cost of production is lowered. a a

One special advantage of this invent on is that an uncarbonized fuel such as bituminous coal or even sawdust or chipped wood may be used instead of coke or charcoal, the raw fuel being carbonized in the stack and the volatile gases being burnt and thus serving as fuel to heat the stack.

ll claim:

1. In an electric furnace of the type specified, an enclosed chamber, an electrode entering therein from above, a passageway in the side wall, a vertical stack at the side of the chamber, into the base of which the passageway enters, a series of vertical; partitions in the stack, supporting a series of alternating ly inclined floors extending from the side walls with outlets at their lower edges to the floor below, with means to pass the gases from the furnace upwardly over the floors in succession.

2. In an electric furnace of the type specified, an enclosed chamber, an electrode entering therein from above, a passageway in the side wall, a vertical stack at the side of the chamber, into the base of which the passageway enters, a series of vertical partitions in the stack, supporting a series of alternatingly inclined floors extending from the side walls with outlets at their lower edges to the floor below, with a series of openings in the partitions forming horizontal flues over each floor, by-pass passages in the end walls of the stack connecting adjacent fines alternate ly adapted to provide a continuouschannel for the gases from the furnace upwardly over the floors in succession to an outlet at the top of the stack.

3. In an electric furnace of the type speci lied, an enclosed chamber, an electrode enter ing therein from above, a passageway in the side wall, a vertical stack at the side of the chamber, into the base of which the passageway enters, a series of vertical partitions in the stack, supporting a series of alternating ly inclined floors extending from the side walls with outlets at their lower edges to the floor below, with means to pass the gases from the furnace upwardly over the floors in succession, and means to feed the ore mixture to be treated downwardly over the floors at a controlled rate.

'4. In an electric furnace of the type specilied, an enclosed chamber, an electrode entering therein from above, a passageway in the side wall, a vertical stack at the side of the chamber, into the base of which the passageway enters, a series of vertical partitions in the stack,,supporting a series of alternatingly inclined floors extending from the side walls with outlets at their lower edges to the floor below, with a series of openings in the partitions forming horizontal fines over each floor by-pass passages in the end walls of the stack connecting adjacent flues alternately, adapted to provide a continuous channel for the gases from the furnace upwardly over the floors in succession to an outlet at the top of the stack, and means to feed the ore mixture to be treated downwardly overthe floors at a controlled rate.

Sill

5. In an electric furnace of the type specified, an enclosed chamber, an electrode entering therein from above, a passageway in the side wall, a vertical stack at the side of the chamber, into the base of which the passageway enters, a series of vertical partitions in the stack, supporting a series of alternatingly inclined fioors extending from the side walls with out-lets at their lower edges to the floor below, with means to pass the gases from the furnace upwardly over the floors in succession, and means to feed air to the gases during their ascent through the stack.

6. In an electric furnace of the type specified, an enclosed chamber, an electrode entering therein from above, a passageway in the side wall, a vertical stack at the side of the chamber, into the base of which the passage- "way enters, a series of vertical partitions in the stack, supporting a series of alternatingly inclined floors extending from the side walls with'outlets at their lower edges to the floor below, with means to pass the gases from the furnace upwardly over the floors in succession, and means to feed air and fuel to the gases during their ascent through the stack.

T. In an electric furnace of the type specified, an enclosed chamber, an electrode entering therein from above, a passageway in the side wall, a vertical stack at the side of the chamber, into the base of which the passageway enters, a series of vertical partitions in the stack, supporting a series of alternatingly inclined floors extending from the side walls with outlets at their lower edges to the floor below, with a series of openings in the partitions forming horizontal flucs over each floor, by-pass passages in the end walls of the stack connecting adjacent flues alternate ly, adapted to provide a continuous channel for the gases from the furnace upwardly over the floors in succession to an outlet at the top of the stack, andmeans to feed the ore mixture to be treated downwardly over the floors at a controlled rate, and means to feed airv to the gases during their ascent through the stack.

8. In an electric fur ace of the type specitied,- an enclosed chamb r, an electrode entering therein from above, a passageway in the side wall, a vertical stack at the side of the chamber, into the base of which the passageway enters, a series of vertical partitions in the stack, supporting a series of alternatingly inclined floors extending from the side walls with outlets at their lower edges to thefloor below, with a series of openings in the partitions forming horizontal flues over each floor, by-pass passages in the end walls of the stack connecting adjacent fliies' alternately, adapted to provide a continuous channel for the gases from the furnaceupwardly over the floors in succession to an outlet at the top of the stack, and means to feed the ore mixture to be treated downwardly over the floors at a controlled rate, and means to feed air and fuel to the gases during their ascent through thestack.

9. In an electric furnace of the type specified, an enclosed chamber, an electrode entering therein from above, a passageway in the side wall, a vertical stack at the side of the chamber, into the base of which the passageway enters, a series of vertical partitions in the stack, su )porting a series of alternatingly inclined fioors extending from the side walls with outlets at their lower edges to the floor below, with means to pass the gases from the furnace upwardly over the floors in succession, and means to feed the ore mixture to be treated downwardly over the floors at a controlled rate comprising a series of rakes adapted to reciprocate on the floors.

10. In an electric furnace of the type specified, an enclosed chamber, an electrode entering therein from above, a passageway in the side wall, a vertical stack at the side of the chamber, into the base of which the passageway enters, a series of vertical partitions in the stack, supporting a series of alternatingly inclined floors extending from the side walls with outlets at their lower edges to the floor below, with means to pass the gases from the furnace upwardly over the floors in succession, and means to feed the ore mixture to be treated downwardly over the floors at a controlled rate, and a series of sliding gates adapted to close the openings of said floors.

11. In an electric furnace of the type specified, an enclosed chamber, an electrode entering therein from above, a passageway in the side wall, a vertical stack at the side of the chamber, into the base of which the passagewayenters, a series of vertical partitions in the stack, su porting a series of alternat ingly inclined fibers extending from the side walls with outlets at their lower edges to the floor below, with means to pass the gases from the furnace upwardly over the floors in succession, and means to feed the ore mixture to be treated downwardly over the floors at a. controlled rate, and poking holes in the side walls adapted to admit pokers to the said floors.

12. In an electric furnace of the type specitied, an enclosed chamber, an electrode entering therein from above, a passageway in the side wall, a vertical stack at the side of the chamber, into the base of which the passageway enters, a series of vertical partitions in the stack, supporting a series of inclined floors alternating from the center and from the side walls with outlets at their lower edges to the floor below, with means to pass the gases from the furnace upwardly over the floors in succession.-

13. In an electric furnace of the type speciified, an enclosed chamber, an electrode entering therein from above, a passageway in the side Wall, leading from the smelting zone of the chamber, a vertical stack at the side of the chamber, into the base of which the passageway enters, a series of Vertical pertitions in the stack, supporting a series of alternatingly inclined floors extending from the side Walls with outlets at their lower edges to the floor below, With means to pass the gases from the furnace upwardly over the floors 10 in succession.

ALFRED STANSFIELD. 

